1. Field of the Invention
The present invention relates to a method for registering (storing) data into a file device and a data retrieval method, and more particularly to a method for registering data into a file device in an information retrieval system for retriving a data record having a designated index from the file device which comprises a record medium which is hard to rewrite recorded information, and a data retrieval method for such registered data.
2. Description of the Prior Art
In a field of office automation, there is an increased need to electronically file a large volume of text as image data by utilizing an optical disk which has a large information storage capacity and can record code data.
The optical disk which can record image data as well as code data and can additionally record newly created data is disclosed in articles entitled "A Large Capacity Optical Disk File Device Capable of Recording Code Information" by Y. Tsunoda et al, NIKKEI ELECTRONICS, Nov. 21, 1983, Nikkei McGrow Hill, pp. 189-213 or "Large Capacity Optical Disc File" by Hiroshi Kitani and Yoshito Tsunoda, Hitachi Review, Vol. 33-No. 3, June 1984; pp. 109-118. The presently practical optical disk device capable of additionally recording data described in the above article has advantages of high recording density and large storage capacity and also has disadvantages of (a) disability of physically erasing data recorded on the disk or rewriting the data with other data, and (b) lower data readout speed than that of a device which uses another recording medium such as a magnetic disk.
The above disadvantage (a) renders it practically difficult to sort code data such as text titles or key words which are stored in the optical disk and used as indices in text retrieval in alphabetic sequence or kana sequence can store them together with image data of the texts in the optical disk, because such index data must be resorted, that is, rearranged on the file or updated each time one or a predetermined number of texts are added to the file. Thus, in the file device which uses such optical disk, when a title of a text is designated to retrieve the corresponding text, all of the text titles registered in the optical disk are sequentially read out and they are compared with the designated title. However, in the retrieval system which reads out all of the text titles, the disadvantage (b) appears dominatingly. As a result, as the volume of data stored increases, the data retrieval time increases, and the operability is lowered in an interactive text retrieval system.